Radio with antenna connector having high and low impedance points

ABSTRACT

A radio transceiver of the present invention includes a transmission line within a housing. The transmission line is comprised of a hollow center conductor and an outer conductor, both connected to a transceiver circuit. The transmission line is also connected to a low impedance connector which is coupled to the housing. A retractable 1/2 wave antenna having an integral matching section will be matched to a transceiver circuit when extended. When the antenna is retracted, the antenna is retracted within the center conductor and acts as a 1/4 wave antenna and will still be matched to the transceiver circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to portable communications equipment thatutilizes retractable or fixed antennas. More particularly the presentinvention relates to a transceiver device compatible with both highimpedance and low impedance connections without having a matchingcircuit or switching means included within the device.

2. Problems in the Art

Many devices such as cellular telephones use a retractable 1/2 waveantenna. This antenna has a high impedance and requires the use of amatching circuit when connected to the transmitter to provide themaximum energy transfer to the antenna. In some prior art devices, themanufacturers add additional space to the device which is required inorder to fit in a matching circuit section that may be external to themain circuit board. Also, when the output power from the transmitter orthe receiver sensitivity is checked by connecting the device to testingequipment, the high impedance matching circuit presents a problem. Theimpedance of most testing equipment is either 50 or 75 ohms and not thehigh impedance required by the matching circuit (typically 600-2,000ohms). If the transceiver performance is measured with this impedancemismatch, significant errors in the measurement will result. Many priorart devices overcome these errors by attaching an additional connector,typically coaxial, to a 50 ohm point on the transceiver circuit toprovide a test point with accurate information. This solution requiresadditional coaxial line, a separate connector, and an electrical ormechanical switch to ensure the proper energy transfer from the printedcircuit board to the chosen connection. These solutions are notdesirable because of the increase in cost and circuit complexity.

Prior art devices using retractable antennas incorporate an internalmatching circuit which connects to the antenna assembly to provide theperformance of a 1/2 wave antenna in the extended position. The problemwith this feature is that the antenna is matched to the impedance of thetransceiver only in the extended position and not in the retractedposition. This creates an impedance mismatch that reduces the efficiencyof the antenna when it is in the retracted position.

OBJECTS OF THE INVENTION

A general object of the present invention is to provide a retractable1/2 wave antenna with an integral matching section.

A further object of the present invention is to provide a transceiverhaving a low impedance connector for attachment to service equipment andexternal antennas.

A further object of the present invention is to provide a transceiverhaving a connector that provides an integral impedance match for highefficiency end-fed 1/2 wave antennas.

A further object of the present invention is to provide a transceiverhaving an antenna connector that requires no electrical or mechanicalswitching inside the transceiver to select the proper impedance asantennas or equipment are interchanged.

A further object of the present invention is to provide a transceiverhaving an antenna connector that allows for the use of fixed replacementantennas (including 1/2 wave and 1/4 wave) without compromisingperformance because of an impedance mismatch.

A further object of the present invention is to provide a transceiverhaving an end-fed 1/2 wave antenna that incorporates an integralmatching section for proper match when extended.

A further object of the present invention is to provide an antenna thatbypasses the integral 1/2 wave matching section for operation as a 1/4wave antenna when retracted.

These as well as other objects of the present invention will becomeapparent from the following specification and claims.

SUMMARY OF THE INVENTION

A radio transceiver of the present invention includes a transmissionline within a housing. The transmission line is comprised of a hollowcenter conductor and an outer conductor, both connected to a transceivercircuit. The transmission line is also connected to a low impedanceconnector which is coupled to the housing.

The present invention also includes a retractable antenna which can becoupled to the low impedance connector. The retractable antenna has anextended position and a retracted position. In the extended position, acontact on the antenna makes electrical contact with the centerconductor of the transmission line. The contact is connected to animpedance matching circuit within the antenna which matches the antennawith the low impedance connection. In this extended position, theantenna acts as a half-wave antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a cellular telephone and anantenna.

FIG. 2 is an exploded perspective view of an antenna of the presentinvention.

FIG. 3 is a sectional view of a retractable antenna in the extendedposition.

FIG. 4 is a sectional view of a retractable antenna in the retractedposition.

FIG. 5 is a view of the antenna disconnected from the antenna connector.

FIG. 6 is a sectional view of an alternative antenna connector and anexternal coax adapter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described as it applies to its preferredembodiment. It is not intended that the present invention be limited tothe described embodiment. It is intended that the invention cover allalternatives, modifications, and equivalences which may be includedwithin the spirit and scope of the invention.

In its preferred embodiment, the present invention applies to aconventional cellular telephone transceiver. Since the present inventionapplies to both radio receivers and transmitters, for purposes of thisapplication, the term "transceiver" shall be deemed to include areceiver, a transmitter, or a combination of the two unless otherwisespecified. FIG. 1 shows a cellular telephone 10 having a housing 12 andan antenna 26. The antenna 26 is electrically connected to the internalcircuitry of the telephone 10 through a connector 14 which threadablyreceives the antenna 26 as will be described in more detail.

The connector 14 and integral antenna 26 consist of a 50 ohm coaxialline 16 that terminates in the connector of the invention. FIG. 3 showsa coaxial line 16 having a center conductor 17 that is attached to acenter conductor tube 18 of the connector 14. The outer shield 20 of thecoaxial line 16 attaches to the outer tube 22 of the connector 14. Thisforms a 50 ohm transmission line with one end terminated in a threadedconnector 24 for attachment to either internal or external 50 ohmantennas as well as external test equipment.

The transmission line described above can be used with a retractableantenna 26 that has an extended position and a retracted position. Inthe extended position, the antenna 26 is extended from the housing 12(FIG. 3) and when retracted, the antenna 26 is retracted within thecenter tube conductor 18 (FIG. 4). The retractable antenna 26 includesan internal impedance matching section 28 which is connected to thecenter conductor 18 through contact 30. The impedance matching circuit28 within antenna 26 allows maximum RF power transfer from the lowimpedance transmission line to the high impedance antenna 26. In thepreferred embodiment, the matching section 28 includes an inductor 32.The inductor 32 can be made from a plated trace on a polymer, a coilinductor, or a printed circuit. The inductor 32 in conjunction with theantenna mount 34 comprises a reactance tuning network that functions asan impedance transformer. This impedance transformer matches the 1/2wave antenna to the 50 ohm transmission line as an integrated unit. Inoperation, the RF signal passes from contact 30 to inductor 32, to theantenna element.

When the antenna 26 is in the retracted position as shown in FIG. 4, thematching circuit 28 including inductor 32 is retracted inside the centerconductor 18 of the transmission line. This arrangement forms a highlycapacitive coupling which makes antenna 26 effectively look like anextension of the transmission line while antenna 26 is in the retractedposition. The upper portion of antenna 26 includes a helical antennaelement 36. In the retracted position, the helical antenna element 36becomes RF coupled to the connector 14. When the antenna element 36 isRF coupled to the connector 14, it can be either electrically connectedor electrically separated from the antenna. The helical antenna 36 thenacts like a quarter-wave antenna. This antenna is an extension of thetransmission line with a capacitive reactive tuning provided by theantenna mount 34.

Therefore, it can be seen that the retractable antenna 26 can beoperated in both the fully extended position as well as the fullyretracted position without an impedance mismatch associated with priorart connectors which are typically high impedance connectors only.

When the retractable antenna 26 is removed from the cellular telephone10, it can be replaced with a fixed length quarter-wave flexibleantenna. The short quarter-wave flexible antenna has a low impedance andis designed to operate in accordance with the transmission linedescribed above. This facilitates maximum electromagnetic energytransfer from the transmission line to the antenna while providing asmall, convenient size for applications where the signal and coverageare sufficient and do not require the superior performance of a longerantenna.

The retractable antenna 28 can also be replaced with a longer moreefficient antenna. A 1/2 wave fixed flexible antenna can be used wherethe performance of a longer more efficient antenna is required. Thisantenna will have an integrated matching section manufactured into theantenna mount so that this antenna, as well as the retractable andquarter-wave fixed antennas may be attached directly to the antennaconnector 14 of cellular phone 10 without the need for changing thematching, switched impedance, circuitry, or any other undesirable costincreasing options that are found in the prior art.

When it is desired to connect test equipment to the transceiver, theantenna can be easily removed and a coaxial connector can be attached tothe transmission line to provide a 50 ohm match to the test equipment.This overcomes one significant disadvantage of prior art devices. Priorart devices provide a retractable antenna connection that is typicallymatched to a high impedance 1/2 wave antenna. This requires the additionof an external antenna connector and the increased complexity of thecircuitry for adaptation to external antennas and test equipment. If theexternal connector is not included in prior art devices, then there is asignificant impedance mismatch that prevents the device from connectingto test equipment for reliable performance measurements.

Sometimes it is desired to connect a cellular phone to an antenna on theexterior of a automobile. The performance of the reception andtransmission of a cellular phone is often impaired when a phone is usedwithin a vehicle. This is caused by the shielding effects of the metalsurfaces of the automobile. By connecting the phone to an exteriorantenna, the undesirable shielding effects are overcome which improvesthe performance significantly. For maximum energy transfer andeffectiveness of the phone, the antenna should be directly attached tothe transceiver. To accomplish this, it is important that the antenna beconnected directly to an RF connector which is properly matched to theantenna to provide the optimum energy transfer to the antenna. Theconnector of the present invention accomplishes this.

FIG. 6 shows an alternative embodiment of the present invention. Atransceiver connector that provides connections for devices havingvarious impedance requirements is shown as connector 40 in FIG. 6. Theconnector 40 is designed to provide a three conductor connection. Theconnector 40 is attached to a printed circuit board within a device suchas a cellular phone 10 to couple RF energy to an antenna or testequipment.

Conductor 42 in FIG. 6 is connected to a high impedance point on theprinted circuit board of the phone 10 through an inductor, forming ahigh impedance connector. Conductor 42 is round and can have threads onits interior surface for threadably receiving a conductor for an antennaor test equipment.

Conductor 44 is connected to a low impedance (50 ohm) point on theprinted circuit board of the phone 10 forming a low impedance connector44. Conductor 44 is also round and can have a threaded interior surfacefor threadably receiving a conductor for an antenna or test equipment.

Ground conductor 46 is connected to the chassis ground of the printedcircuit board circuitry to form an attachment point for the ground whenan external adapter 48 is attached to the device. The capacitive elementof the circuit is comprised of the relationship of connections 42, 44,and 46.

When a high impedance antenna is desired, the antenna will be attachedto the high impedance connector of the phone 10 through connection 42.Connection 42 is smaller in diameter than section 44, so the highimpedance antenna will not make contact with the low impedanceconnection 44. In this configuration, the current will pass throughconnection 42 and into the end-fed 1/2 wave high impedance antenna andis then radiated into space.

When a low impedance antenna is desired, the low impedance antenna willbe connected to telephone 10 through the low impedance connection 44.The antenna will not make contact with the high impedance connection 42.This provides optimum energy transfer when a low impedance quarter-waveis connected to the connector 40.

When it is desired to connect test equipment or an external antenna tothe phone 10, an external adapter 48 is attached to the connector 40 ofthe phone 10. The low impedance connection 44 will be connected to acenter conductor 50 of the adapter 48 to provide a 50 ohm connectionpoint to the center conductor 50 of the test equipment or externalantenna. The ground connection 46 is connected to the external adapterground 52 to provide the ground for the coaxial adapter 48.

The connections 42 and 44 are both hollow to provide clearance for usewith a retractable antenna. So, like the embodiment described in FIGS.1-5, the embodiment of FIG. 6 accomplishes the objectives of the presentinvention.

The preferred embodiment of the present invention has been set forth inthe drawings and specification, and although specific terms areemployed, these are used in a generic or descriptive sense only and notused for purposes of limitation. Changes in the form and proportion ofparts as well as in the substitution of equivalents are contemplated ascircumstances may suggest or render expedient without departing from thespirit or scope of the invention as further defined in the followingclaims.

What is claimed is:
 1. An antenna connector for use with a radio havinghigh and low impedance points comprising:a first conductor coupled to aground forming an attachment point for the ground at said connector; asecond conductor coupled to a first impedance point of said radio, saidsecond conductor being hollow, said second conductor having a firstdiameter; and a third conductor coupled to a second impedance point ofsaid radio, said third conductor being hollow, said third conductorhaving a second diameter, said second diameter being smaller than saidfirst diameter, said third conductor and said second conductor beingdisposed proximate each other in a co-axial relationship wherein anexternal center conductor may be coupled to either of said second orthird conductors depending on the diameter of said external centerconductor, said second and third conductors being arranged such that aretractable antenna may be slidably received through said second andthird connectors.
 2. The antenna connector of claim 1 further comprisingan external coaxial adapter coupled to said connector, said coaxialadapter having a ground coupled to said first conductor, said coaxialadapter having a center conductor coupled to said second or thirdconductor of said antenna connector.